The best lens is the lens you have if you only have one lens. However, if you have more than one, which one should you use?
My favorite is my 24-70mm lens. It gives me some ability to zoom and also go wide. To help you choose here are some ideas to consider. A wider lens will give you a better opportunity to capture more on the screen than a long lens. If you are considering a prime lens, then I would not recommend a longer than a 100mm lens.
If you want to use a longer lens, start with a wider angle lens as the fireworks start to get an idea of where to expect the fireworks to appear. With a longer lens, you will need to be more precise to capture the fireworks.
Another approach for a longer lens is to start with your first best guess for the location of the fireworks in the sky and adjust to capture what you want. Most firework shows last 15 to 20 minutes so you will have time to adjust. Once you have that location locked in, don't be tempted to try to swing the tripod for fireworks close to the ground. You will most likely miss them and lose your position in the sky for the high fireworks.
I outline the settings I use in my PDF located here:
I have a series on several techniques for firework photography.
I also have blog posts to go along with the videos above and you can find them here:
Blog Posts Series: